北上台风云系结构变化的遥感定量特征指标研究及应用

RESEARCH AND APPLICATION OF REMOTE SENSING QUANTITATIVE CHARACTERISTIC INDEXES OF THE STRUCTURAL CHANGE OFTHE CLOUD SYSTEMS OF NORTHWARD TYPHOONS

关键词:  北上台风  卫星遥感  结构诊断  强度变化

Key words:  northward typhoon  satellite remote sensing  structure diagnosis  intensity change

摘要:

定量诊断分析北上台风的云系结构特征对于预报有重要意义，研究选取2011—2020年16个北上台风，定义南北对称度因子S1和一三象限对称度因子S2，作为反映北上台风云系结构的指标。当S1<0时，通常台风南侧和西南侧的云量较多，并常与季风云系相连，台风一般表现为“9”字型结构；当S1>0时，通常台风北侧和东北侧的云量较多，台风南侧的云系减弱，台风一般表现为“6”字型结构。台风北上过程中由S1<0向S1>0转变，在云系结构特征上表现为由“9”字型结构转化为“6”字型结构。而这种结构特征的转变初始表现为台风核心区域内第一象限云量增多并向东北方向伸展，同时第三象限对流云衰减以及云量减少，此时，一三象限对称度因子S2>0并快速增大，台风有快速减弱的趋势。南北对称度因子和一三象限对称度因子作为北上台风云系结构诊断分析的两个重要指标，为台风强度、降雨的监测和预报形成了定量参考。

Abstract:

Quantitative diagnosis and analysis of the cloud structure characteristics of northward typhoons is of great significance for forecasting. In the present study, sixteen northward typhoons occurred during 2011—2020 are selected to define the North-South symmetry factor S1 and the one-three quadrant symmetry factor S2 as the indexes to reflect the cloud structure of northward typhoons. When S1 < 0, there were usually more clouds on the south and southwest sides of the typhoons, which were often connected with the monsoon system, and the typhoons generally showed a “9” shaped structure. When S1 > 0, there were more clouds on the north and northeast sides of the typhoons, the cloud systems on the south side of the typhoons weakened, and the typhoons generally showed a “6” shaped structure. During the northward movement of the typhoons, S1 transited from < 0 to > 0, and the “9” shaped structure turned to a “6” shaped structure. At the same time, the convective cloud in the third quadrant decayed and the total cloud amount decreased. The one-three quadrant symmetry factor S2 became greater than 0 and increased rapidly, and the typhoons weakened rapidly. The North-South symmetry factor and the one-three quadrant symmetry factor are two important indexes for the diagnosis and analysis of the structure of the cloud systems of northward typhoons and they constitute a quantitative reference for the monitoring and forecasting of typhoon intensity and rainfall.